"Write down the addition table for $\mathbb Z/4$ "
Could someone please give one or two hints? And what does them mean with $\mathbb Z/4$? They have never used that notation before. Do them just mean the integer divided by $4$ or what? I don't have any answer to this question so I would need someone to check my solution after the hint(s) :)
The addition table for $\mathbb{Z}_4$ is
$$ \begin{array}{c|cccc} & 0 & 1 & 2 & 3 \\ \hline 0 & 0 & 1 & 2 & 3 \\ 1 & 1 & 2 & 3 & 0 \\ 2 & 2 & 3 & 0 & 1 \\ 3 & 3 & 0 & 1 & 2 \\ \end{array} $$
and the multiplication table for $\mathbb{Z}_4$ is
$$ \begin{array}{c|cccc} & 0 & 1 & 2 & 3 \\ \hline 0 & 0 & 0 & 0 & 0 & \\ 1 & 0 & 1 & 2 & 3 & \\ 2 & 0 & 2 & 0 & 2 & \\ 3 & 0 & 3 & 2 & 1 & \\ \end{array} $$